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Message-ID: <1541548114.196084.195.camel@acm.org>
Date: Tue, 06 Nov 2018 15:48:34 -0800
From: Bart Van Assche <bvanassche@....org>
To: Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org
Cc: linux-nvdimm@...ts.01.org, tj@...nel.org,
akpm@...ux-foundation.org, linux-pm@...r.kernel.org,
jiangshanlai@...il.com, rafael@...nel.org, len.brown@...el.com,
pavel@....cz, zwisler@...nel.org, dan.j.williams@...el.com,
dave.jiang@...el.com
Subject: Re: [driver-core PATCH v5 5/9] driver core: Establish clear order
of operations for deferred probe and remove
On Mon, 2018-11-05 at 13:12 -0800, Alexander Duyck wrote:
> One change I made in addition is I replaced the use of "bool X:1" to define
> the bitfield to a "u8 X:1" setup in order to resolve some checkpatch
> warnings.
Please use "bool X:1" instead of "u8 X:1". I think it was a bad idea to make
checkpatch complain about "bool X:1" since "bool X:1" should only be avoided
in structures for which alignment must be architecture-independent. For struct
device it is fine if member alignment differs per architecture. Additionally,
changing "bool X:1" into "u8 X:1" will reduce performance on architectures that
cannot do byte addressing.
> static void __device_release_driver(struct device *dev, struct device *parent)
> {
> - struct device_driver *drv;
> + struct device_driver *drv = dev->driver;
>
> - drv = dev->driver;
> - if (drv) {
> - while (device_links_busy(dev)) {
> - __device_driver_unlock(dev, parent);
> + /*
> + * In the event that we are asked to release the driver on an
> + * interface that is still waiting on a probe we can just terminate
> + * the probe by setting async_probe to false. When the async call
> + * is finally completed it will see this state and just exit.
> + */
> + dev->async_probe = false;
> + if (!drv)
> + return;
>
> - device_links_unbind_consumers(dev);
> + while (device_links_busy(dev)) {
> + __device_driver_unlock(dev, parent);
>
> - __device_driver_lock(dev, parent);
> - /*
> - * A concurrent invocation of the same function might
> - * have released the driver successfully while this one
> - * was waiting, so check for that.
> - */
> - if (dev->driver != drv)
> - return;
> - }
> + device_links_unbind_consumers(dev);
>
> - pm_runtime_get_sync(dev);
> - pm_runtime_clean_up_links(dev);
> + __device_driver_lock(dev, parent);
> + /*
> + * A concurrent invocation of the same function might
> + * have released the driver successfully while this one
> + * was waiting, so check for that.
> + */
> + if (dev->driver != drv)
> + return;
> + }
>
> - driver_sysfs_remove(dev);
> + pm_runtime_get_sync(dev);
> + pm_runtime_clean_up_links(dev);
>
> - if (dev->bus)
> - blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
> - BUS_NOTIFY_UNBIND_DRIVER,
> - dev);
> + driver_sysfs_remove(dev);
>
> - pm_runtime_put_sync(dev);
> + if (dev->bus)
> + blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
> + BUS_NOTIFY_UNBIND_DRIVER,
> + dev);
>
> - if (dev->bus && dev->bus->remove)
> - dev->bus->remove(dev);
> - else if (drv->remove)
> - drv->remove(dev);
> + pm_runtime_put_sync(dev);
>
> - device_links_driver_cleanup(dev);
> - arch_teardown_dma_ops(dev);
> + if (dev->bus && dev->bus->remove)
> + dev->bus->remove(dev);
> + else if (drv->remove)
> + drv->remove(dev);
>
> - devres_release_all(dev);
> - dev->driver = NULL;
> - dev_set_drvdata(dev, NULL);
> - if (dev->pm_domain && dev->pm_domain->dismiss)
> - dev->pm_domain->dismiss(dev);
> - pm_runtime_reinit(dev);
> - dev_pm_set_driver_flags(dev, 0);
> + device_links_driver_cleanup(dev);
> + arch_teardown_dma_ops(dev);
> +
> + devres_release_all(dev);
> + dev->driver = NULL;
> + dev_set_drvdata(dev, NULL);
> + if (dev->pm_domain && dev->pm_domain->dismiss)
> + dev->pm_domain->dismiss(dev);
> + pm_runtime_reinit(dev);
> + dev_pm_set_driver_flags(dev, 0);
>
> - klist_remove(&dev->p->knode_driver);
> - device_pm_check_callbacks(dev);
> - if (dev->bus)
> - blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
> - BUS_NOTIFY_UNBOUND_DRIVER,
> - dev);
> + klist_remove(&dev->p->knode_driver);
> + device_pm_check_callbacks(dev);
> + if (dev->bus)
> + blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
> + BUS_NOTIFY_UNBOUND_DRIVER,
> + dev);
>
> - kobject_uevent(&dev->kobj, KOBJ_UNBIND);
> - }
> + kobject_uevent(&dev->kobj, KOBJ_UNBIND);
> }
This patch mixes functional changes with whitespace changes. Please move the
whitespace changes into a separate patch such that this patch becomes easier
to read.
> void device_release_driver_internal(struct device *dev,
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 1b25c7a43f4c..fc7091d436c2 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -1043,14 +1043,15 @@ struct device {
> struct iommu_group *iommu_group;
> struct iommu_fwspec *iommu_fwspec;
>
> - bool offline_disabled:1;
> - bool offline:1;
> - bool of_node_reused:1;
> + u8 offline_disabled:1;
> + u8 offline:1;
> + u8 of_node_reused:1;
> #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
> - bool dma_coherent:1;
> + u8 dma_coherent:1;
> #endif
> + u8 async_probe:1;
The new async_probe field can be changed from multiple threads. Concurrent
changes of a bitfield are only safe if these are serialized in some way.
Please document the locking requirements for the async_probe bitfield in
device.h.
Thanks,
Bart.
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